Synthesis of glycerol



Patented Dec. 11, 1923.

UNITED STATES PATENT-OFFICE.

HARRY ESSEX AND ALGER L. WARD, OF WILMINGTON, DELAWARE, ASSIGNDBS 1'0 E;I DU PON'I' DE NEMGUBS & COMPANY, OF WILMINGTON, DELAWARE, A GOR-I'OBATION OF DELAWARE SYNTHESIS OF GLYCEROL.

No Drawing.

To all whom it may concern:

Be it known' that we, HARRY Essex and of glycerol from allyl chloride.

One object of our invention is to provide an efiicient and inexpensiveprocess of syn-' thesizing glycerol.

Another object of our invention is to provide an improved process ofconverting allyl chloride into glycerol dichlorhydrin by the chemicaladdition of hypochlorous acid, in order to render this reactioncommercially feasible as a step in the manufacture of glycerol.

Previous attempts have been made to convert allyl chloride into glycerolby chemical addition of chlorine to allyl chloride to form 1, 2,3-trichlorhydrin, and by subsequent hydrolysis of the 1, 2,3-trichlorhydrin to lycerol, but difliculties encountered rendered theprocess impracticable'.

To obviate these dlfiiculties, it occurred to us that it might bevossible to add hypochlorous acid to ally chloride and hydrolyze thedichlorhydrins so produced to glycerol according to the equations.

CH,cl.CH=CH +HOCl=' CH Cl.CHCl.C-H,OH.

We discovered that dichlorhydrin could be hydrolyzed to glycerol muchmore easily ods, is very unstable, decomposing in the light and in thepresence of salts and metals,

forms are purc asable at a low price, as

added slowl conditions t e allyl chloride combines with than couldtrichlorhydrin. Hypochlorous acid, however, is an expensive reagent whenprepared. according to the ordinary -meth-' Application filed September27, 1919. Serial No. 826,818.

sodium hypochlorite in electrolytic'bleach (eau de l'abarraque) orcalcium hypochlorite in chloride of lime. Salts of hypochlorous acidare, however, in general poor'sources for a solution of the free acid.If it is attempted to displace hypochlorous acid from its salts by theaddition of a stronger acid it is found that the free hypochlorous acidliberated reacts with the remaining hypochlorite and with a velocitywhich is proportional to the Sig-11816 of the concentration of the freeh-ypoc orous acid. In the case of sodium hypochlorite, the reactions arefrom which it is apparent that no matter how small the quantity of freeacid present it is regenerated again and again and the above cycle ofreactions proceeds until .no hypochlorite remains. These reactionsexplain the well known and rapid autodecomposition of h pochloritesolutions which contain evensma l quantitiesof free hypochlorous acid.I11 continuing our investigations we discovered that the hypochloritesmay serve excellently as a source of hypochlorous acid for the aforesaidreaction with allyl chloride provided the operations are so conductedthat both reactions, i. e., the liberation of hypochlorous acid and theaddition of hypochlorous acid to allyl chloride, take practicallysimultaneously. This we ave effected in the following manner: An excessof allyl chloride is added to a water solution of a salt of hypochlorousacid and the mixture vigorous y agitated. An acid, acid anhydrid, orsolution of an acid salt is then to the mixture. Under these thehypochlorous acid almost as fast as the latter s formed and theconcentration of lace hypochlorous acid is kept solow that the lossresulting from the 2HClO=NaClO,+2HCl-is negligible.

The dichlorhydrins so produced remain insclution or, if in'suflicient.water is present, may separate as a-heavy oily liquid. Dichlorhydrinsremaining in the solution may, if desired, be extracted with ether.

The second part of our invention lies in reactionNaOCl-{-' I thediscovery that the-:glycerine 'dichlor;

r in excess to a. solution containin hydrins produced by the action ofhypechlorous acid on allyl chloride and consistingprincipally of theisomer with the formula CH CLCHCLCH OH, may be con verted into'glycerine with high yields (95% of the theoretical), and that theconversion is readil effected without isolating the dichlorhyd i'insfrom the reaction mixture; To accomplish this result it is merelynecessary to heat the solution containing the dichlorhydrins withhydroxide,-carbonate or other substance to combine with the hydrochloricacid liberated. The reaction equation of the hydrolysis is- CH CLCHCLCHOH+2H O:

CH OH.CHO'H.CH OH+2HCL In an embodiment of these discoveries whichappears particularly promising as aallyl chloride, which C., is addedsodium hypochlorite and the mixture vigorously stirred Carbon dioxide isthen admitted to the mixed liquids, liberating hypochlorou commercialprocedure, is a liquidboiling at about 46 acid according to theequationtilled 0 through a fractionating column and v the dichlorhydrinsare hydrolyzed to glycerine, the sodium carbonate assisting thisreaction by removing the hydrochloric acid as it is formed. In somecases it may be desirable to add more sodium carbonate to "thehydrolyzing solution to increase the yield of glycerine or the velocityof the hydroly- SIS.

The process may be illustrated more in detail by the following examplesI. 225 parts by Wei ht of allyl chloride are added to 4000 parts of asolution containing 215 parts by weight of soduim hypochlorite. Thereaction vessel is surrounded with ice and the contents stirredvigorously. Carbon dioxide gas is then bubbled through the liquid untila test shows only traces of hypochlorous acid. The flow of carbondioxide is then discontinued and the stirring stopped. 400 parts ofsodium carbonate are thenadded, the reaction vessel Water, and ametallic oxide,

' olefines to form provided with a reflux condenser and the contentskept at boiling temperature for seven hours. About 1 part of allylchloride may distill off during this period. The water solutionremaining in the reaction vessel should contain, according to ourexperiments, about 200 parts of glycerine, a'yield of 82% of thetheoretical based on the allyl chloride used.

II. 225 pounds of allyl chloride are added to 220 pounds of sodiumhypochlorite in water solution, the mixture vigorously stirred andcarbon dioxide passed in until hypochlorites have nearly or completelydisappeared. 156 pounds of sodiumcarbonate are then ,added and thetemperature raised to boiling and kept there for several hours. Ifchlorates are absent the glycerin may be recovered by concentration anddistillation.

If chlorates are present they should be reduced, for obvious reasons,before it is attempted to recover the glycerine. The reactions are 2-2CH,OH.CHOH.GH OH+4NaCl+200 As indicated in the above examples, theproportions of sodium carbonate may vary widely, but should preferablybe between about 150 and 400 parts for each 225 parts of allyl chlorideused.

Our invention has been described with special reference tochloropropylene (allyl chloride) as the chlorolefine with which theprocess may be started, this constituting at the present time a valuableapplication of our invention; but it will be understood that otherchlorolefines may be used such as chlorobutylenes, chloramylenes, etc.We have also discovered that instead of chloro-substitutedolefines,-there may be used other halolefines as bromopropylene, the useof the latter in the formation of 1-bromo-2 chlorhydrin havingadvantages for certain purposes not possessed b chloropropylene.

'As further adaptations of the principles elucidated above, it maybementioned that by analogous methods, hypobromous acid or hypoiodousacid ma be added to halogen poly alohydrins and the resulting polyhalo yrins may be hydrolyzed to polyhydric alcohols. For example, hypobromousacid may be added to allyl bromide to form glycerol dlbromhydrinshydrolyzed to glycerme'.

We claim 1. The process which comprises inducing a reaction between ahalolefine and aqueous hypochlorous acid in the presence of an alkali-'metal carbonate to form a mixture containing correspondinghalogen-substituted chlorhydrins and said carbonate, and heatingglycerol dibromhydrins and V the v said mixture until saidhalogen-substituted chlorhydrinsha-ve been hydrolyzed to polyhydricalcohols.

- gradually adding thereto a substance capable of reacting with saidhypochlorite to form hypochlorous acid and an alkali-metal salt untilsubstantially all of the chlorolefine present has been converted by thehypochlorous acid into the corresponding .polychlorhydrin, and thenheating the resulting mixture in the presence of an agent capable ofaccelerating hydrolysis until said poly chlorhydrin becomes hydrolyzedtoa polyhydric alcohol.

4. The process which comprises agitating a mixture-of a chlorolefine anda water solution of a hypochlorite .while adding carbon dioxide theretoto form hypochlorous acid at such a rate that said hypochlorous acidbecomes combined with the chlorolefine about as fast as it is formed,and then heating the resulting polychlorhydrin' in the presence of waterand carbonate formed during the preceding step until saidpolychlorhydrin becomes hydrolyzed to. a polyhydric alcohol. 7

5. The process which comprises agitating a mixture of a chlorolefine anda water solu- .stituted chlorhydrins,

tion ofsodium hypochlorite while adding carbon dioxide thereto to formhypochlorous acid at such a rate that said hypochlorous acid becomescombined with the chlorolefine about as fast as it is formed, and thenheating the resulting polychlorhydrin in the presence of water andsodium carbonate formed during the preceding ste until saidpolychlorhydrin becomes hydro polyhydric alcohol.

6. The process which comprises'inducin a reaction between an allylhalide an aqueous hypochlorous acid to form a mixture containingcorresponding halogen-suband heating said mixture until saidhalogensubstituted chlorhydrins have been hydrol zed to glycerol.

7. The process whic comprises inducing a; reaction between allylchloride and aqueous'hypochlorous acid to form a mixture containingdichlorhydrins, and heating said mixture until said dichlorhydrinsbecome hydrolyzed to glycerol.

8. The process which comprises agitating a mixture of allyl chloride anda water solution of a hypochlorite while gradually e and aqueous.

yzed to a adding thereto a substance capable of reacting with saidhypochlorite to form hypochlorous' acid substantially all of the allllylchloride present has been converted by t e h and t on heating theresulting mixture in the presence of an agent capable of accelerating'hydrolysis until said dichlorhydrin becomes hydrolyzed to glycerol.

9. The process which comprises agitating hlorous acid into--dichlorhydrin,'

a mixture of allyl chloride and a water solution of a hypochlorite whileadding carbon dioxide thereto to form hypochlorous acid bined with theallyl chloride about as fast as it is formed, and then heating theresulting dichlorhydrin in the presence of water and carbonate formedduring the preceding step until said dichlorhydrin becomes hydrolyzed toglycerol.

10. The process which comprises agitating a mixture of allyl chlorideand a water solution of sodium hypochlorite while adding carbon dioxidethereto to form. hypochlorous acid at such a rate that said acid becomescombined with the allyl chloride about. as fast as it is formed, andthen heating-the resulting dichlorhydrin in the presence of at such arate thatsaid acid becomes comwater and sodium carbonate until said.

dichlorhydrin glycerol.

11. .The process of producing glycerol which' comprises cooling andvigorously stirrin a mixture of 225 parts of allyl chlori e and about4000 parts of water solution containing from about 215 to 220 parts ofsodium hypochlorite, while passing carbon dioxide thereinto until a testshows only a small percentage of hypochlorous acid, then adding fromabout 150 to 400 parts of sodium carbonate, heating the resultingmixturecontaining dichlorhydrins at about a boiling temperature tohydrolize the dichlorhydrins to glycerol while distilling off anyunchanged allyl chloride, and then removi salts which are present. 12.he process of producing glycerol which comprises heating a glyceroldichlorhydrin in the presence of both water and a substance capable ofpromoting hydrolysis of said d ichlorhydrin.

13. The process of producing glycerol which comprises heating a glyceroldichlorbecomes hydrolyzed to hydrin in the presence of both water and analkali-forming metal carbonate.

14. The process of ing temperature a water solution of glyceroldichlorhydrins and sodium carbonate until hydrolysis of thedichlorhydrins is substan tially complete.

producing glycerol which comprisesheating at'about the boil-' '15. Theprocess which comprises agitating ble of reacting with said salt to formhypohalous acid until substantially all of the halolefine present hasbeen converted by the hypohalous acid into the correspondingpolyhalohydrins, and then heating the resultin mixture in the presenceof-an agent capab e of accelerating hydrolysis until saidpolyhalohydrins become hydrolyzed to a polyhydric alcohol.

16. The process which comprises agitating a mixture of a halolefine anda water solution of a salt 'of a lraypohalous acid while adding carhondioxi e thereto to form halous acid at .such a rate that said hypohalousacid becomes combined, about as fast as it is formed, with saidhalolefine,

and then heating the resulting polyhalohydrins in the presence-of waterand of HARRY ESSEX.

ALGER L. WARD.

